CIDR Block Rule doesn't seem to work

I have an entry under Screened IPs to Block 223.176.0.0/12. Had a new spammer create an account from 223.176.61.159. Are there other admin settings that affect these rules being active? Or, what is going on here? This isn’t the only example.

hmmm, I’m not sure if that CIDR is correct. have a look here:

https://www.ipaddressguide.com/cidr

Based on;

the range this spammer’s IP belongs to, and therefore I am trying to block is;

223.176.0.0 - 223.191.255.255

We have garbage–and only garbage not legitimate posts–coming in from other IPs in this range.